A PDE-based Equivalent Source and Type Conversion Method for Magnetic Measurement Data

Abstract

The present invention provides a PDE-based magnetic measurement data equivalent source polarity and type conversion method, including: S1, obtaining magnetic field data d 0 , and establish a terrain relief surface according to the terrain height information of the area where the magnetic field data is located; S2, determine the spatial range of grid division, and perform non-uniform multi-layer grid division; S3, according to the magnetic inclination angle, magnetic declination angle and Magnetic induction, for magnetic field data d 0 Carry out PDE three-dimensional inversion calculation with depth regularization factor, positive constraint term and regularization term, and obtain the multi-layer equivalent source model of magnetic anomalies; S4. Given different geomagnetic pole parameters, use multi-layer equivalent source The model carries out the three-dimensional forward calculation of the magnetic field of the nonlinear PDE, and obtains one or more of the polarized data, the total field data of the magnetic anomaly, the component data of the magnetic anomaly and the data of the magnetic gradient tensor. The beneficial effect of the invention is that the self-adaptive and high-precision conversion calculation of polarity and data type can be performed on underground magnetic anomaly data in a complex environment.

Description

technical field [0001] The invention relates to the technical field of geophysical surveying, in particular to a PDE-based method for converting the equivalent source polarity and type of magnetic survey data. Background technique [0002] In geomagnetic detection, people usually detect the total field anomaly of the magnetic field, but in actual data interpretation, it is often necessary to convert these data into required parameters and types, such as the conversion of different magnetization directions (polarized data) , magnetic field components, conversion of tensor data, etc. The main challenge of magnetic field data type conversion lies in the undulating measurement surface of aeromagnetic (terrestrial magnetic survey) and the irregular measurement position of data (non-grid measurement), the traditional data type conversion And chemical pole computing cannot process these data, and the data conversion method of traditional single-layer, double-layer, and three-layer ...

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Problems solved by technology

[0002] In geomagnetic detection, people usually detect the total field anomaly of the magnetic field, but in actual data interpretation, it is often necessary to convert these data into required parameters and types, such as the conversion of different magnetization directions (polarized data) , magnetic field components, conversion of tensor data, etc. The main challenge of magnetic field data type conversion lies in the undulating measurement surface of aeromagnetic (terrestrial magnetic survey) and the irregular measurement position of data (non-grid measurement), the traditional data type conversion And chemical pole computing cannot process these data, and the data conversion method of traditional single-layer, double-layer, and three-layer equivalent sources has low precision of the processing results and cannot meet the application requirements

[0003] Existing literature 1 "Dampney, C.N.G. THE EQUIVALENT SOURCE TECHNIQUE [J]. geophysics, 1969, 34(1): 39." proposed the equivalent source method for the first time, using virtual field sources to simulate measured anomalies, which can be used for potential field data Space continuation (including surface continuation), gradient calculation, and component conversion, etc.; selecting a single-layer equivalent source and arranging it near the surface is the main feature of the equivalent source method, for example, literature 2 "Li Y.Reduction to the poleusing equivalent sources[J].SEG Technical Program Expanded Abstracts,1999,19(1):2484. "Achieved the Polarization Method of Low Latitude Magnetic Anomaly by Setting a Single Layer Equivalent Source in a Limited Depth, Literature 3" Huang Yijian, Wang Wanyin, Yu Changchun. Data processing and conversion of 3D random point potential field using equivalent source method[J]. Advances in Geophysics, 2009(01):101-107." Using a single-layer equivalent source to realize the magnetic field data However, due to the limitations of observational data, the near-surface single-layer equivalent source model cannot completely simulate the deep field source information, so that the potential field reconstructed by the equivalent source will be distorted during continuation; in order to ensure the calculation Efficiency and high-precision reconstruction of the potential field, the multi-layer equivalent source method is a relatively reasonable choice, literature 4 "Li D., Q.Liang, J.Du, S. Sun, Y. Zhang, C. Chen, 2019, Transforming total-field magnetic anomalies into three components using dual-layer equivalent sources, Geophysical Research Letter, 47(3), e2019GL084607." Divide underground equivalent sources into two layers, Literature 5 "Li Duan, Chen Chao, Duan Jinsong et al. Multi-layer equivalent source surface magnetic anomaly conversion method[J]. Geophysical Journal, 2018, 061(007): 3055-3073.” proposed a method of dividing the underground equivalent source into three layers to realize the magnetic field data conversion

[0004] The application of these technologies enables people to use the equivalent source technology to perform polarization and data type conversion calculations for ground magnetic data, but there are the following problems: 1) The equivalent source grid has only three layers at most, and the grid section In the existing technology, due to the limited number of layers of equivalent sources and the unreasonable grid division of underground space, the accuracy and speed of magnetic field data type conversion and polarization are affected; 2) each equivalent source needs to be separately estimating the depth position of the layer, and then placing it separately; 3) Using the linear forward modeling method and the linear model inversion method to calculate the equivalent source, the anti-interference ability and calculation accuracy are poor

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